Circuit interrupter protective device

ABSTRACT

A circuit interrupter protective device responsive to abnormal currents in conductors of an electrical distribution system characterized by a circuit breaker within a first insulating housing and having a mechanism for opening and closing separable contacts which mechanism comprises a releasable member movable between latched to unlatched positions, trip means comprising a stationary magnetic structure for each conductor as well as a coil and core assembly, an armature therefor, a trip bar movable to unlatch the circuit breaker mechanism and biased in the latched position, lever means associated with the stationary magnetic structure for moving the trip bar to the unlatched position, the lever means comprising the armature and being movable in response to abnormal currents in at least one of the conductors, the lever means being biased away from the core assembly, and means for increasing the electrical current range between maximum and minimum air gaps of the magnetic circuit.

United States Patent Salvati et al.

[ Mar. 12, 1974 CIRCUIT INTERRUPTER PROTECTIVE DEVICE [75] Inventors:John G. Salvati, Beaver Falls; Paul Skalka, Beaver, both of Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Mar. 29, 1973 [21] Appl. No.: 346,230

[52] US. Cl 335/176, 335/42, 335/192 [51] Int. Cl. HOlh 9/00 [58] Fieldof Search 335/42, 45, 176, 173, 174, 335/192; 200/166 M [56] ReferencesCited UNITED STATES PATENTS 3,260,822 7/1966 Stephenson et a1 .Q 335/42Primary ExaminerI-Iarold Broome Attorney, Agent, or Firm-L. P. Johns [57] ABSTRACT A circuit interrupter protective device responsive toabnormal currents in conductors of an electrical distribution systemcharacterized by a circuit breaker within a first insulating housing andhaving a mechanism for opening and closing separable contacts whichmechanism comprises a releasable member movable between latched tounlatched positions, trip means comprising a stationary magneticstructure for each conductor as well as a coil and core assembly, anarmature therefor, a trip bar movable to unlatch the circuit breakermechanism and biased in the latched position, lever means associatedwith the stationary magnetic structure for moving the trip bar to theunlatched position, the lever means comprising the armature and beingmovable in response to abnormal currents in at least one of theconductors, the lever means being biased away from the core assembly,and means for increasing the electrical current range between maximumand minimum air gaps of the magnetic circuit.

8 Claims, 6 Drawing Figures I47 '4' I37 I43 I29 '45 IOI\ %83 136 I34 I320 A H9 83b I 1 I03 690 Ill I25. I ll? 7 ||3\:\ I .09 O VL IIE l f & I2369 PATENTED MR 12 l974 SHEET 2 [IF 3 FIGZ FIGS

I07 LY CIRCUIT INTERRUPTER PROTECTIVE DEVICE CROSS REFERENCE TO RELATEDAPPLICATIONS This invention is related to that disclosed in theapplication of Albert E. Maier and William I. Stephenson, Jr., Ser. No.345,394, filed Mar. 27, 1973.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionpertains to a protective device for a circuit interrupter and moreparticularly it pertains to a monitoring means within an insulatinghousing for increasing the spread between maximum and minimum air gapsin a magnetic circuit.

2. Description of the Prior Art Generally, circuit breakers thatcomprise overcurrent protective devices have external mounting means forsuch devices on the circuit breaker housing such as disclosed in U.S.Pat. No. 3,530,414. Circuit breakers of that type have functionedsatisfactorily for responding to such abnormal currents as overcurrents,ground fault currents, and short circuits that occur in an electricaldistribution system. However, it has been found that certaindisadvantages result from that type of construction including theinability to increase the current spread between minimum and maximum airgaps in the magnetic circuit. I

SUMMARY OF THE INVENTION In accordance with this invention, it has beenfound that the foregoing disadvantages may be overcome by providing aprotective device for a circuit interrupter which device comprises astationary magnetic structure for each conductor of an electricaldistribution system and comprising a coil and core assembly, anarmature, a trip bar movable to effect tripping of the circuit breakermechanism and being biased in the latched position, the lever meansassociated with each stationary magnetic structure for moving the tripbar to the unlatched position, the lever means comprising the armatureand being movable in response to abnormal currents in at least one ofthe conductors, the lever means comprising a lever which is biased awayfrom the core assembly, and means for spreading the range between theminimum and maximum air gaps in the magnetic circuit.

The advantage of the device of this invention is that it provides for amore compact tripping unit as well as a more efficient unit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view ofa multi-pole circuit breaker;

FIG. 2 is a vertical sectional view taken on the line 11-11 of FIG. 1;

FIG. 3 is a vertical sectional view taken on the line IlIllI of FIG. 1;

FIG. 4 is a vertical sectional view taken on the line lV--IV of FIG. 3;

FIG. 5 is a vertical sectional view taken on the line VV of FIG. 3; and,

FIG. 6 is a plan view of the trip device shown in FIGS. 2-5.

DESCRIPTION OF TI-IE PREFERRED EMBODIMENTS In FIG. 1, a circuit breakeris generally indicated at 3 and it comprises an insulating housing 5 anda circuit breaker mechanism 7 supported within the housing. The housing5 comprises an insulating base 9 and an insulating cover 11.

The circuit breaker mechanism 7 comprises an operating mechanism 13, anda latch and trip device 15. Except for the latch and trip device, thecircuit breaker 3 is of the type that is generally described in thepatent to Albert R. Cellerini et al., U.S. Pat. No. 3,287,534 issuedNov. 22, 1966. The circuit breaker 3 is a threepole circuit breakercomprising three compartments disposed in side-by-side relationship. Thecenter pole compartment (FIG. 1) is separated from the two outer polecompartments by insulating barrier walls formed with the housing base 9and cover 11. The operating mechanism 13 is disposed in the center polecompartment and is a single operating mechanism for operating thecontacts of all three pole units.

Each pole unit comprises a stationary contact 21 that is fixedly securedto a rigid main conductor 23 that in turn is secured to the base 9 bybolts 25. In each pole unit, a movable contact 27 is secured, such as bywelding or brazing, to a contact arm 29 that is mounted on a switch arm31 by a pivot pin 33. The arms 29 and 31 for all three of the pole unitsare supported at one end thereof and rigidly connected on a commoninsulating tie bar 35 by which the arms of all three pole units move inunison. Each of the contact arms 29 is biased about the associated pivotpin 33 by means of a spring 37 to provide contact pressure in the closedposition.

The operating mechanism 13 actuates the switch arms 31 between open andclosed positions. The mechanism comprises a pivoted formed operatinglever 39, a toggle comprising two toggle links 41 and 43, overcentersprings 45 and 47, and a pivoted releasable cradle or arm 49 controlledby the trip device 15. An insulating shield 51 for substantially closingan opening 53 in the cover 11, is mounted on the outer end of the operating lever 39 and has an integral handle portion 55 extending outthrough the opening to enable manual operation of the breaker. Thetoggle links 41 and 43 are pivotally connected together by a knee pivotpin 57. The toggle link 41 is pivitally connected to the releasable arm49 by a pin 59, and the toggle link 43 is pivotally connected to theswitch arm 31 of the center pole unit by a pin 61. The overcentersprings 45 and 47 are connected under tension between the knee pivot pin57 and the outer end of the operating lever 39. The circuit breaker ismanually operated to the open position by movement of the handle portion55 in a counterclockwise direction to the off position, which movementactuates the overcenter springs 45, 47 to collapse the toggle links 41and 43 to the position shown in FIG. 1, and opening movement of thecontact arm 29 for all of the pole units in a manner well known in theart.

The circuit breaker is manually closed by reverse movement of the handleportion 55 from the off position to the on position, which movementcauses the springs 45, 47 to move overcenter and straighten the togglelinks 41, 43, thereby moving the contact arm 29 for all of the poleunits to the closed position as shown in broken line position.

The trip device 15 serves to effect automatic release of the releasablecradle or arm 49 and opening of the breaker contacts for all of the poleunits, in response to predetermined overload conditions in the circuitbreaker through any or all pole units of the circuit breaker, in amanner described hereinbelow.

The circuit through each pole unit extends from a right-hand terminal 63through the conductor 23, the contacts 21, 27, the contact arm 29, aflexible conductor 65, that is secured to the contact arm 29, aconductor 67, a trip conductor 69, and to a left-hand terminal connector71. Bolt means 73 secure one end of the trip conductor 69 to theconductor 67 and the other end of the trip conductor 69 is disposedbetween a backup plate 75 and the terminal 71 where it is secured inplace by mounting bolt 77 of the terminal 71.

As shown in FIGS. 2-6 the latch and trip device 15 comprises a moldedinsulating housing base 81 and a molded insulating housing cover 79secured to the base to enclose a molded insulating trip bar 83 that iscommon to all three of the pole units. As shown in FIG. 3, the base 81includes a pair of spaced partitions 85 and 87 which are verticallydisposed and integral with the base for separating the interior of thehousing into three compartments, each compartment containing one of thethree poles. In a similar manner, the cover 79 is provided withpartitions corresponding to partitions 85 and 87 and having matingsurfaces therewith in a manner similar to the mating surfaces of theperipheral surfaces of the base 81 and cover 79 as indicated by aparting line 89 (FIG. 6).

As shown in FIG. 3, the partitions 85 and 87 have notches 91 and 93,respectively, which together with flat surfaces of the cover 79 serve asjournals for round shaft portions 95 and 97 of the trip bar 83.Accordingly, when the housing base 81 and cover 79 are assembled, theyretain the trip bar 83 in place, whereby the trip bar is free to rotateon an axis extending through the shaft portions 95 and 97. As shown moreparticularly, in FIG. 5, each section of the trip bar 83 located withinthe space compartments of the housing comprise upper and lower portions83a and 83b, which are above and below the axis of rotation of the tripbar. Each upper portion 83a is provided with an adjusting screw and nutassembly 99 which cooperates with a bimetal member 101 (FIG. foradjusting the spacing between the upper ends of the bimetal member andthe trip bar portion 83a in response to the degree of deflection of theupper end of the member 101 toward the member 83a, whereby the trip bar83 is rotated clockwise by the bimetal member and thereby trips thecircuit breaker to the open position. The lower end portion 83b of thetrip bar 83 is preferably provided with a drive screw 103 by whichcontact is made with an adjoining member for similar rotation of thetrip bar in the manner to be described hereinbelow.

As shown more particularly in FIG. 5, the trip conductor 69 includes aninverted U-shaped intermediate portion 69a which constitutes a singleloop of a stationary magnetic structure. Stationary magnetic structurealso comprises a magnetic core 105, a U-shaped frame 107 having a pairof spaced flanges 109 one of which is shown in FIG. 5, and an armature111. The assembly of the intermediate U-shaped portion 69a, the core105, and the intermediate portion of the frame 107 together with thelower portion of the bimetal member 101 are secured in place by suitablemeans such as rivets 113 on the housing base 79. The lower end portionof the bimetal member 101 is in surface-to-surface contact with theconductor 69, whereby upon the occurrence of a low persistent overloadcurrent below a predetermined value of, for example, ten times normalrated current, the bimetal member 101 is heated and deflects to theright through an air gap dependent upon the setting of the adjustmentscrew 99. Thus, when a low persistent overload current occurs, the tripbar 83 is actuated to trip the circuit breaker.

The armature 111 is disposed between the space flanges 109 of theU-shaped frame 107 and is pivotally mounted therein to rotate about anaxis 115 near the lower end of the armature. For that purpose, thearmature 111 is preferably mounted by suitable means such as rivets 117on a support lever 119 having oppositely extending out-turned lugs 121which are seated in corresponding openings 123 in the flanges 109. Eachflange 109 is also provided with a V-shaped notch 125 into which edgeportions of the lever 119 and armature 111 extend. The notches 125thereby limit movement of -the assembly of the lever 119 and armature111 when the armature is attracted toward the core 105. Accordingly, theassembly of the lever 119 and armature 111 which is biased in theclockwise direction by coil springs 127 (FIG. 3) is movablecounterclockwise against the springs to engage the drive screw 103 andthereby rotates the trip bar 83 clockwise. When an overload currentabove a value such, for example, as ten times normal rated current or ashort circuit current occurs, the stationary magnetic structure isenergized and the armature 111 is attracted toward the core 105 causinginstantaneous release of the releasable arm 49 and opening of thecontacts 21 and 27.

In addition to the foregoing, means are provided for adjusting thespacing between the armature 111 and the core 105, whereby upon maximumspacing of the armature from the core, a greater current overload isrequired to attract the armature toward the core. Conversely, when thespacing is reduced, a smaller overload current is required to actuatethe trip bar 83. For that purpose an adjustment bracket 128, having alower end disposed over the upper end of the lever 119, is mountedwithin the housing and is provided with calibration means including acalibration screw 131 at the upper end of the bracket 128. As shown inFIG. 3, each bracket 128 includes a notch 133 on each opposite sidethereof which notch is seated in corresponding projections 135 of thehousing base 79.

In accordance with this invention the bracket 128 comprises means forincreasing the current spread between maximum and minimum air gaps ofthe magnetic circuit. For that purpose the bracket 128 is provided withmeans for positively adjusting and maintaining the armature in theproper position for the desired air gap. The means comprise a tensionspring 129 and spaced prongs or fingers 130, 132, 134. The outer fingers130 and 134 extend over one side of the armature 111 and the middlefinger 132 extends on the other side of the armature. That is the middlefinger 132 is located on the core side of the armature. The fingers 130,132, 134 may be an integral part of the bracket 128, or preferably partof a separate member that is fixedly attached to the bracket by suitablemeans such as rivets 136.

The fingers 132 and 134 are members that act to reduce the air gap whenthe adjusting screw 131 rotates the armature assembly clockwise. Themiddle finger 132 acts as a leaf spring that flexes at different degreesdepending upon the air gap setting. The middle finger 132 exerts anadditional force against the armature; that is, in addition to theforces exerted by the compression springs 127. In the maximum air gapposition of the armature, the leaf spring finger 132 is bent more thanin the minimum air gap position of the armature. Thus, the middle finger132 exerts a greater force on the armature in the maximum air gapsetting than it does in the minimum air gap setting. This means that theover-current spread (5 to times normal rating) to trip the breakermagnetically between minimum and maximum air gap settings is thereforebetter controlled.

The finger 132 flexes in response to the adjustment and position of thebracket assembly 128, not in response to the armature movement. Thefinger 132 exerts a force on the armature opposite to that of thesprings 127. When the armature 111 is at a maximum air gap, thecompression springs 127 are at their minimum values. Conversely, whenthe armature is at the minimum air gap, the spring are in maximumcompression and therefore exert a greater force on the armature than thefinger 132.

The force exerted on the armature by the finger 132 is greater in themaximum air gap setting than the force exerted on the armature atminimum air gap setting. The reason for that is that the bend in themiddle finger is greater at maximum air gap than the bend is on minimumair gap. The greater the bend the greater is the force that it exerts onthe armature. Indeed, the amount of bend on the middle finger 132 canalso be controlled by manually bending the finger in one direction oranother to create more or less bend when assembled with the armature.

The tension spring 129 pulls the upper portion of the bracket assembly128 against the camming portion of an adjusting knob 137. The tensionspring 129 also retains the upper portion of the bracket assembly 128stationary as the middle finger bends, such as during calibrationadjustments. When the armature is pulled in by magnetic forces, thebracket assembly pivots about the pivot 135. When in the unactuatedposition, the armature is retained in the preselected position by thefinger 132 or one side and the fingers 130 and 134 on the other side.

The adjusting knob 137 is seated within the top end of the housing baseand is provided with a lower end portion having a cam surface. Inasmuchas the bracket 128 is biased counterclockwise about its pivot point bythe springs 127 of the lower lever 119, the calibration screw 131 rideson the cam surface of a lower camming portion 139 of the adjusting knob137.

As shown in FIGS. 3 and 5, each adjusting knob 137 includes a flange141, the lower surface of which includes spaced notches 143. An indexmember 145 is disposed below the flange 143 and is provided with aprojection 147 for engaging one of the spaced notches 143 as thecalibrating screw 147 is rotated to the desired position. Accordingly,the desired spacing between the armature 111 and the core 105 isestablished by rotation of the adjusting knob 137.

Since the housing cover 79 is used to hold the brackets 128 in place, itis necessary to assemble the trip unit completely before calibrating theposition of the bracket 128. For that reason, a removable flexibleshield 149 is disposed in an access opening 151 of the cover 79 in orderto turn the calibrating screws 131 and 99. When the calibration is made,the shield 149 is replaced in the opening. The mechanism by which thereleasable arm 49 is released is shown in FIGS. 2, 4 and 6. Themechanism includes the trip bar 83, a trip lever 153, and a latch lever155. A U-shaped mounting frame 157 is mounted on the base 81 with spacedupright sides 157a and 157b providing mounting support for the levers.The trip lever 153 includes a U-shaped por tion 159 at the lower endwhich portion is mounted on a pivot pin 161 which extends from the side1570 of the frame. The U-shaped lower portion of the lever maintains thelever upright adjacent the frame side 157a. The upper end of the triplever 153 includes a flange 163 which engages a notch 165 on the tripbar 83. As shown in FIG. 4 a portion of the trip bar extends through anopening 167 in the insulating base 81.

The latch lever includes down-turned portions 155a and 155b which aremounted on a pivot pin 169 the opposite ends of which are secured in thesides 157a and 157k of the frame 157. A spring 171 is mounted on the pin169 and has end portions engaging the levers 153 and 155 for biasing thelevers in the latched positions. When the releasable arm 49 is in thelatched position as shown in FIG. 1, the arm which is pivoted on a pivotpin 173 is secured in the latched position below the lever 155 andapplies a rotatable force thereon. The latch lever 155 is prevented fromturning due to engagement of the lower end of the lever on a pin 175which is mounted in the U-shaped portion 159 of the trip lever 153. As aresult of the rotating force on the latch lever 155, the trip lever 153is biased clockwise and is prevented from movement by engagement of theflange 163 in the notch of the trip bar 83. When the trip bar is rotatedclockwise, the flange 163 is dislodged from the latched position withinthe notch 165 and the trip lever 153 rotates clockwise to move the pinfrom engagement with the lower end of the latched lever 155. As a resultthe latch lever 155 is free to rotate about the pin 169 and therebyunlatch the releasable arm 49 from the latched position.

As shown in FIG. 3, a projection 177 extends from the upper corner ofthe trip bar portion 83a which projection is aligned with an aperture179 (FIG. 4) in the housing base 79. By extending a pin through theopening 179 (FIG. 2) and pressing against the projection 177, the tripbar may be tripped manually.

Accordingly, the device of the present invention provides an new andnovel trip structure for a circuit breaker which comprises means forincreasing the electrical current range between maximum and minimum airgaps of the magnetic circuit.

What is claimed is:

1. A circuit interrupter protective device for responding to abnormalcurrents in the conductors of an electrical distribution system and foractuating a circuit interrupter to open upon the occurrence ofpredetermined operating conditions, comprising a circuit breaker havinga first insulating housing, a circuit breaker mechanism within thehousing and comprising separable contacts adapted to be connected aspart of the distribution system, the circuit breaker mechanismcomprising a releasable member movable from a latched position to effectopening of the contacts, a

latch lever movable between latched and unlatched positions of thereleasable member and being biased in the latched position, a stationarymagnetic structure for each conductor of the distribution system andcomprising a coil and core assembly, an armature, a trip bar movable tounlatch the latch lever and being biased in the latched position, levermeans associated with each stationary magnetic structure for moving thetrip bar to the unlatched position, the lever means comprising thearmature and being movable in response to abnormal currents in at leastone of the conductors, the lever means comprising an adjusting bracketwhich is biased away from the core assembly, the adjusting bracketcomprising three spaced fingers, one finger being flexible and engagingthe side of the armature facing the core assembly for maintainingpredetermined spacings between the armature and the core assembly duringnormal current flow, and the flexible finger being yieldable to magneticforces attracting the armature to the core assembly during theoccurrence of an overload in the conductors.

2. The circuit interrupter protective device of claim 1 in which themagnetic structure, the trip bar, the lever means, and the spaceadjusting means are mounted within a second insulating housing, and thesecond insulating housing being mounted within the first insulatinghousing.

3. The circuit interrupter protective device of claim 2 in which thearmature is mounted on a lever which is pivoted at a location remotefrom the bracket.

4. The circuit interrupter protective device of claim 3 in which theflexible finger engages the end portion of the lever remote from thepivot location.

5. The circuit interrupter protective device of claim 4 in which theother fingers engage the side of the lever opposite that engaged by saidflexible finger.

6. The circuit interrupter protective device of claim 2 in which meansare provided for adjusting the spacing between the armature and the coreassembly.

7. The circuit interrupter protective device of claim 6 in which acalibrating screw is mounted on the bracket and the means for adjustingthe spacing comprises an adjustable knob haivng a cam surface engagingthe calibrating screw to effect movement of the lever to a desiredposition.

8. The circuit interrupter protective device of claim 7 in which atension spring extends between the bracket and the second insulatinghousing for holding the calibrating screw in engagement with the camsurface.

1. A circuit interrupter protective device for responding to abnormalcurrents in the conductors of an electrical distribution system and foractuating a circuit interrupter to open upon the occurrence ofpredetermined operating conditions, comprising a circuit breaker havinga first insulating housing, a circuit breaker mechanism within thehousing and comprising separable contacts adapted to be connected aspart of the distribution system, the circuit breaker mechanismcomprising a releasable member movable from a latched position to effectopening of the contacts, a latch lever movable between latched andunlatched positions of the releasable member and being biased in thelatched position, a stationary magnetic structure for each conductor ofthe distribution system and comprising a coil and core assembly, anarmature, a trip bar movable to unlatch the latch lever and being biasedin the latched position, lever means associated with each stationarymagnetic structure for moving the trip bar to the unlatched position,the lever means comprising the armature and being movable in response toabnormal currents in at least one of the conductors, the lever meanscomprising an adjusting bracket which is biased away from the coreassembly, the adjusting bracket comprising three spaced fingers, onefinger being flexible and engaging the side of the armature facing thecore assembly for maintaining predetermined spacings between thearmature and the core assembly during normal current flow, and theflexible finger being yieldable to magnetic forces attracting thearmature to the core assembly during the occurrence of an overload inthe conductors.
 2. The circuit interrupter protective device of claim 1in which the magnetic structure, the trip bar, the lever means, and thespace adjusting means are mounted within a second insulating housing,and the second insulating housing being mounted within the firstinsulating housing.
 3. The circuit interrupter protective device ofclaim 2 in which the armature is mounted on a lever which is pivoted ata location remote from the bracket.
 4. The circuit interrupterprotective device of claim 3 in which the flexible finger engages theend portion of the lever remote from the pivot location.
 5. The circuitinterrupter protective device of claim 4 in which the other fingersengage the side of the lever opposite that engaged by said flexiblefinger.
 6. The circuit interrupter protective device of claim 2 in whichmeans are provided for adjusting the spacing between the armature andthe core assembly.
 7. The circuit interrupter protective device of claim6 in which a calibrating screw is mounted on the bracket and the meansfor adjusting the spacing comprises an adjustable knob haivng a camsurface engaging the calibrating screw to effect movement of the leverto a desired position.
 8. The circuit interrupter protective device ofclaim 7 in which a tension spring extends between thE bracket and thesecond insulating housing for holding the calibrating screw inengagement with the cam surface.